Experimental study on the explosion characteristics of hydrogen-methane premixed gas in complex pipe networks

To explore the overpressure evolution laws and flame propagation characteristics in complex pipe networks after the addition of hydrogen to methane, we experimentally studied the explosive pressure wave and flame wave propagation laws for three different premixed gas mixtures with hydrogen-methane concentrations of 0, 10% and 20% when the equivalence ratio was 1. Experimental results indicate that the maximum explosion overpressure of the premixed gas increases with increasing distance from the explosion source, and it shows a gradually decreasing trend. In the complex pipe network, an overpressure zone is formed in the B–E–H and D–E sections of the network. The flame temperature is superimposed with the superimposition of the pressure, showing a trend of first increasing, then decreasing, then increasing, and finally decreasing in the complex pipe network. The flame arrival time increases with increasing distance, and the maximum flame speed shows a decreasing trend. The peak overpressure and maximum flame velocity of the premixed gas under a hydrogen volume fraction of 20% are 1.266 MPa and 168 m/s. The experimental research results could provide important theoretical guidelines for the prevention and control of fuel gas explosions in urban pipe networks.

Explosion-Suppression Characteristics of Nonmetallic Spherical Spacers on Propane-Air Mixtures in Confined Space

The explosion-suppression effects of NSSs on overpressures, flame propagation and flame tip velocities were explored under the initial pressures of 0.2 MPa, 0.3 MPa and 0.4 MPa. All experiments tested in a constant volume combustion bomb (CVCB). Explosion reaction of premixed propane–air gas in a new designed CVCB filled with nonmetallic spherical spacers (NSSs) was analyzed. The results showed that overpressures decreased under the different initial pressures. With the increase of filling density, the overpressure decreased, the time to reach explosion overpressure decreased, and the decay rate of explosion overpressure increased. It was also found that the explosion-suppression effects of NSSs on pressures. Flame front could be captured by high-speed schlieren photography. Combustion phenomena were captured including flame propagation, corrugated laminar flame, jet flame, corrugated turbulent flame as well as tulip flame under different initial pressures. Flame tip velocities also were captured. The results demonstrate that flame tip velocities decreased with the increase of filling densities. However, compared with unfilled CVCB, flame tip velocities increased after filling NSSs in CVCB under different initial pressures. NSSs suppressed the explosion overpressure in the cylinder, and promoted the flame propagation. In both cases, NSSs played a dual role. The suppression effect of NSSs was affected by both its suppression and promotion effect on the explosion. This work provides a scientific basis for the effective prevention of explosion accidents with propane–air premixtures and the development of explosion-suppression products.

Experimental Study On The Explosion Characteristics of Hydrogen-methane Premixed Gas in Complex Pipe Networks

To explore the overpressure evolution laws and flame propagation characteristics in complex pipe networks after the addition of hydrogen to methane, we experimentally studied the explosive pressure wave and flame wave propagation laws for three different premixed gas mixtures with hydrogen-methane concentrations of 0, 10% and 20% when the equivalence ratio was 1. Experimental results indicate that the maximum explosion overpressure of the premixed gas increases with increasing distance from the explosion source, and it shows a gradually decreasing trend. In the complex pipe network, an overpressure zone is formed in the B-E-H and D-E sections of the network. The flame temperature is superimposed with the superimposition of the pressure, showing a trend of first increasing, then decreasing, then increasing, and finally decreasing in the complex pipe network. The flame arrival time increases with increasing distance, and the maximum flame speed shows a decreasing trend. The peak overpressure and maximum flame velocity of the premixed gas under a hydrogen volume fraction of 20% are 1.266 MPa and 168. The experimental research results could provide important theoretical guidelines for the prevention and control of fuel gas explosions in urban pipe networks.

Computational Fluid Dynamics (CFD) Modeling and Analysis of Hydrocarbon Vapor Cloud Explosions (VCEs) in Amuay Refinery and Jaipur Plant Using FLACS

Process safety helps prevent the unexpected and unplanned release of flammable and toxic chemicals, leading to poisonous gas clouds, fires, and explosions. Vapor cloud explosions (VCEs) are among the most severe hazards to humans and the environment in process facilities. Therefore, process safety demands to use best and reliable techniques to model VCEs in process industries and storage tanks of flammable chemicals. In this regard, the Computational Fluid Dynamics (CFD) models are more appropriate, as these models provide three-dimensional (3D) modeling of all sequences of events in an accident. In this study, CFD is used to model VCE in two industrial accidents: the Amuay refinery disaster (happened in 2012) and the Indian Oil Corporation’s (IOC) Jaipur terminal (2009). This work studies 3D CFD modeling of flammable cloud explosion in the real-time configuration for both accidents. FLACS (FLame ACceleration Simulator), a CFD software, is used to simulate the loss of hydrocarbon containment, cloud formation, and explosion in both industrial case studies. The ignition locations and grid sizes were varied to analyze their influence on explosion overpressure, temperature, vapor velocity, and fuel mass. This work also investigated the effect of geometry complexity on the explosion. Results showed that, as opposed to the coarse grid, the fine grid provides more precision in the analysis. The study also reveals an explosion overpressure of the order 4–15 bar (g) for the given case studies. This study’s results can help perform a qualitative and quantitative risk assessment of the Amuay refinery accident and Jaipur fire. The simulation of different scenarios can help develop and improve safety guidelines to mitigate similar accidents.

Numerical study of external explosion characteristics induced by indoor natural gas vented explosion

Purpose The purpose of this paper is to ascertain the harm to personnel and equipment caused by an external explosion during natural gas explosion venting. The external explosion characteristics induced by the indoor natural gas explosion are the focal points of the investigation. Design/methodology/approach Computational fluid dynamics technology was used to investigate the large-scale explosion venting process of natural gas in a 6 × 3 × 2.5 m room, and the characteristics of external explosion under different scaled vent size (Kv = Av/V2/3, 0.05, 0.08, 0.13, 0.18) were numerically analyzed. Findings When Kv = 0.08, the length and duration of the explosion fireball are 13.39 and 450 ms, respectively, which significantly expands the degree and range of high-temperature hazards. The suitable flow-field structure causes the external explosion overpressure to be more than twice that indoors, i.e. the natural gas explosion venting overpressure may be considerably more hazardous in an outdoor environment than inside a room. A specific range for the Kv can promote the superposition of outdoor rupture waves and explosion shock waves, thereby creating a new overpressure hazard. Originality/value Little attention has been devoted to investigating systematically the external explosion hazards. Based on the numerical simulation and the analysis, the external explosion characteristics induced by the indoor large-scale gas explosion were obtained. The research results are theoretically significant for mitigating the effects of external gas explosions on personnel and equipment.

ANALYSIS OF MATHEMATICAL RELATIONS FOR CALCULATION OF EXPLOSION WAVE OVERPRESSURE

The explosion of an explosive system causes primary and secondary effects on people and objects near its site. The most devastating is the pressure effect of the explosion, especially the overpressure. Individual parameters of pressure wave (overpressure size, duration impulse) can be determined by mathematical or virtual modeling or can also be measured under real conditions. The authors focused on the parameters of the positive phase of the shock wave propagating from the source of the explosion towards the object. The article covers the description and analysis of selected mathematical relations, which are used to determine the magnitude of the explosion overpressure. The results are based on selected formulas. The source of the explosion referred in the study is an explosive system containing a reference explosive trinitrotoluene (TNT). TNT is a military explosive that is used as a reference explosive in technical standards dedicated to the certification of explosion-proof elements, and at the same time, a TNT equivalent is known to allow the mass of an explosive charge to be recalculated. The results obtained by mathematical modeling according to individual approaches have been compared and the possibilities of using computational models in the area of security management and education of security managers have been identified. The results of the study confirm that prediction of pressure wave parameters at different distances and weights can assist security managers in creating attack scenarios and designing a suitable object protection system.